So are different intervalls of oil change between Australia and Europe - and yet, even in the 90s, people were able to keep that in mind.
We got taught to be helpless by the industry, so they can help us out. If that mindset would have existed in the 60s, 70s, then there would not be a "true to OEM" aftermarket available for car parts. We need to get back to that.
industry is pretty damn good at figuring out what customers actually want, instead of just what customer say they want and then don't actually buy.
cars are the way they are because that's what the overwhelming majority of car buyers actually want. The average driver doesn't want their car spitting out error codes, they want a check engine light to tell them to take it to a mechanic, and any information beyond that is confusing.
The check engine light tells you nothing. It tells your local mechanic nothing. Do you can't get the problem fixed easily or cheaply.
What it does, is force you to take the car to a dealer, who has the specialist, proprietary equipment needed to interpret the fault. And these gatekeepers will charge you a fat premium for that.
So no. I don't think this design choices are driven by a desire to serve the customer.
most people take it to a mechanic instead, because that's what they'd rather do.
There are plenty of proprietary codes that might set a malfunction light and not show up on an OBD reader, or not be interpreted by it.
(there are tools that reverse-engineer the proprietary protocols that can show those codes, but they aren't $20 - more like $200 and up)
I really don't see why you're defending hiding information. Even for someone who doesn't want to mess around and would just take it to a dealer, making the information available without the need for a code reader will not hurt in any way.
So yes - it’s the industry that got us screwed.
New car buyers are 10-15% of the annual car market (US).
The other 85-90% of people are stuck with whatever the other people bought.
The industry makes cars more expense because it makes them more money. Some consumers want big and flashy. Some want cheap and reliable with enough space for cargo and passengers. Only one of those is being served currently. The rest of the industry is drifting to the up market with even the base trim being too expensive for many consumers.
Looking at current sales trends isn't adequate to gauge consumer demand for products that don't exist because they can't be purchased and something else has to take it's place.